SE-C-523 690 discloses a centrifugal separator which is intended for cleaning of a gas containing liquid impurities in the form of oil particles and/or oil mist. The gas outlet for the cleaned gas extends in the known centrifugal separator from a lower part of the separation space. Immediately above the gas outlet, there is a shield element which extends into the separation space. Above the shield element at a distance therefrom, there are a number of outlet holes for discharge of the separated oil from the separation space. The separated oil is caught by the inner wall of the separation space and flows downwardly towards the outlet holes. The technique disclosed in SE-C-523 690 is based on the phenomenon that the shield element will create an annular gas cushion immediately above the shield element, and that this gas cushion will stop the downwardly flowing oil at the level of the upper end of the gas cushion and at the level of the outlet holes so that the oil may be discharged through the outlet holes.
The applicant has found that a part of the downwardly flowing oil will pass the gas cushion and the shield element, which means that this part of the oil will follow the cleaned gas out from the centrifugal separator through the gas outlet.
The outlet holes of the known centrifugal separator are equidistantly located along the periphery of the casing. This means that the oil that is discharged through the holes has to be collected outside the casing for the transport to a common outlet.